A basic wireless charging system may include a wireless power transmitter unit (PTU) and a wireless power receiving unit (PRU). A PRU may be implemented in a mobile computing device, such as a laptop, tablet or smart phone, which can be placed on a charging mat equipped with a PTU. The PTU may include a transmit (Tx) coil and a PRU may include a receive (Rx) coil. The Tx and Rx coils may be referred to as induction coils. In typical induction chargers the Tx coil creates an alternating electromagnetic field and the Rx coil takes power from the electromagnetic field and converts it back into electrical current to charge the battery and/or power the device. The two induction coils in proximity combine to form an electrical transformer.
The charging session handshaking between the PRU and the PTU is implemented over a side communication channel, such as a Bluetooth Low Energy link (BLE). When a charging session starts, the PTU sends power beacon pulses intended to provide the PRU with sufficient energy to turn on the side channel circuitry and send advertisement packets to the PTU. These beacon signals are short, and have limited amount of power to turn on the side channel circuitry.
The same numbers are used throughout the disclosure and the figures to reference like components and features. Numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.